The demand for greater quantities of information and data transfer to and from residential as well as business users continues to grow faster than supply can keep up with it. This information demand is being supplied in a variety of forms consisting of telephone systems of various forms, cable systems, hybrid fiber/cable systems, and wireless systems. This invention relates to a Local Multi-Point Distribution System (LMDS) intended to provide such services as broadcast video, video-on-demand, multimedia capability, interactive video, high speed data, telephony, and computer data links as examples. The system can provide a wireless interface from, for example, a local TELCO central office (CO), or a cable Head End office, in all cases, from a facility in a system defined as a “Head End” facility. FIG. 1 illustrates such a system. Note that the system consists of three basic components, i.e., a Head End facility, a system of Base Stations, and a multitude of system service Subscribers. The overall system is made up of a geographical structure of non-overlapping cells, wherein each geographical cell consists of some several hundred Subscribers all of whom are supported by one Base Station. Some number of Base Stations are all interfaced to a single Head End.
As shown in FIG. 1, the Head End collects all signals to be distributed throughout the system thereby forming a star configuration. The Head End at the center of the star, the Base Stations surround the Head End and the Subscribers surround the Base stations. As examples of signals collected, digital video may be gathered via satellite links, a telephone system interface may be provided via Class 5 switches, and high rate digital data networks may be interfaced via a high rate data switch. The data to/from the Head End is distributed to the system of local base stations each assigned to serve its geographical “cell” of subscribers.
While the description presented herein refers generally to a “micro cellular” system, which is defined as a system of cells of 5 km radius or less, the invention is equally applicable to a “macro cellular” system, herein defined as a system of cells of radius greater than 5 km.
The unique features embodied in the invention described herein include the following:
1) A micro cellular system of signal distribution for local multi-point distribution system (LMDS) application.
2) A micro cellular system of signal distribution with 100% frequency re-use of one with a four sector rectangular array of cells and with a six sector rectangular array of cells.
3) A micro cellular system of signal distribution with 100% frequency re-use of one with a four sector rectangular array of cells with a six sector rectangular array of cells incorporating the use of cross polarization isolation between sectors of adjacent cells operating at the same frequencies.
4) A micro cellular system of signal distribution with 200% frequency re-use of one with a four sector rectangular array of cells and with a six sector rectangular array of cells incorporating the use of cross polarization isolation between sectors of adjacent cells operating at the same frequencies, and operating with increased sectorization of the cells.
5) A micro cellular system of signal distribution with 100% frequency re-use of one with a four sector rectangular array of cells and with a six sector rectangular array of cells incorporating the use of intelligent frequency management between sectors of adjacent cells operating at the same frequencies.
6) A system capable of providing, for example, analog video broadcast, digital video in either broadcast or on-demand modes, interactive multimedia services, high rate digital data services, telephony, and in home monitoring systems such as might be employed for power meter reading or home security alarm systems.
7) A frequency reference technique whereby the Subscribers equipment is synchronized to the Base Station high stability sources and thereby minimize a) equipment implementation costs, b) signal acquisition times, and c) signal bandwidth overhead requirements to accommodate hardware frequency instability characteristics.
8) A closed loop Subscriber transmit power control technique whereby the Subscriber received power levels at the Base Station are all received at the same level thereby minimizing the possibility of any mutual interference between Subscriber signals, and eliminating the need for any significant AGC requirements in the Base Station RF receiving equipment.
9) A closed loop subscriber transmit timing control technique whereby the Subscriber received signal timing as received at the Base Station is adjusted by the Base Station in increments equal to the transmit signal symbol period to ensure the reception of all signals with a minimum of mutual interference from other Subscriber signals.
10) The optional use of antenna polarization diversity as a means of minimizing adjacent cell interference signals and increasing the total achievable capacity of the system.
11) A TDMA signaling structure which maximizes the transmit signaling format efficiency.
12) A signaling system operating within the ATM system specifications enabling an efficient utilization of system signaling capacity, as well as a highly flexible and adaptable signaling format allowing efficient redistribution of system bandwidth width in real time as the Subscriber data requirements change.
13) An order wire channel capability and signalling format which enable the entry and exit of Subscribers easily and efficiently in real time as the Subscriber needs and Subscriber population changes.
14) An order wire channel capability and signalling format which easily and efficiently accommodates real time Subscriber requests for changes in the services required, additions to the services required, and the execution of control functions to the services being provided, e.g., “VCR” like controls to a video being viewed such as the “pause” function.
15) A frequency plan which on the Down Stream provides orthogonal OC-1 channels spaced at F frequency steps where F is the transmission data rate of the Down Stream channel, and on the Up Stream provides ½ OC-1 channels spaced at F where 2F′=F.
16) The optional use of a two-way satellite link interface from the Head End to the Base Station of a cell which is geographically remote from the central cell system.
17) The incorporation of maximally efficient burst modem techniques thereby enabling reception of multiple mutually asynchronous time multiplexed signals each emanating from different transmitting sources by a single receiver thereby simplifying the design and cost of both the transmitting and receiving equipment.
18) The use of asynchronous transfer mode over a wireless medium for high speed data delivery incorporating the implementation of a highly efficient transmit data frame format which partitions the frame into five different types of data and containing the following characteristics and attributes:                a) A medium access control method employing time division multiplexing on the down stream and time-division multiple access on the up stream and where the up stream frame timing is synchronized to the down stream frame timing;        b) Use of a frame start ATM cell on the down stream as a synchronization mechanism for the up stream frame timing;        c) Use of a region of the up stream frame consisting of a group of contiguous net entry slots for asynchronous access by new subscribers entering the network after power on;        d) Use of a region of the up stream frame consisting of a group of contiguous slots for random access transmissions of subscriber service requests;        e) Use of a portion of the up stream frame for polling of Subscribers for the purpose of gathering power meter data, home security alarm monitoring, and health, status data on the operational system hardware;        f) Use of a remainder of the frame for the communication of data in the ATM mode.        